The present invention relates to a semiconductor integrated circuit device manufacturing art, particularly to an art to be effectively applied to a method for forming a hole or trench (hereafter referred to as hole or the like) in the manufacturing process of a semiconductor integrated circuit device.
The method for forming a hole or the like studied by the present inventors is described below. That is, an etching mask is formed on a layer insulating film and then, the layer insulating film exposed beyond the etching mask is removed through etching by using a fluorocarbon-based gas and an etching gas containing oxygen to form a hole. In this case, however, such problems occur that a part of the hole becomes thick (bowing) and an etching mask is shaved (decrease of selection ratio). By considering these problems, it is effective to reduce the quantity of oxygen to a fluorocarbon-based gas in an etching gas and improve the deposition property of a polymer layer. However, when improving the deposition property, a new problem occurs that etching does not progress (etch stop). Therefore, at the initial stage of etching, the quantity of oxygen is slightly decreased and then increased while finely adjusting the above quantity of oxygen so that the above mentioned bowing does not occur or the selection ratio does not decrease.
The present inventors, however, finds that the above art for forming a hole or the like has problems that it is more difficult to form a hole or the like as the aspect ratio of the hole or the like increases or the adjacent interval between holes or the like decreases.
Moreover, the present inventors have examined publicly-known examples from the viewpoint of a method for forming a hole or the like. The art of this type is disclosed in, for example, the official gazette of Japanese Patent Laid-Open Publication No. 10-209124. That is, an art is disclosed in which a hole is drilled by removing approx. 80% of the total thickness of an inter-layer oxide film through etching at a strong anisotropy though the etching selection ratio between the inter-layer oxide film and a lower titanium-nitride film is low at the first stage and removing the remaining inter-layer oxide film at a high etching selection ratio though anisotropy is weak at the second stage when drilling a through-hole from which a part of the titanium-nitride film on the inter-layer oxide film.
It is an object of the present invention to provide an art capable of forming a hole or trench having a high aspect ratio.
The above and other objects and novel features of the resent invention will become more apparent from the description of this specification and the accompanying drawings.
Typical ones of the aspects of the present invention disclosed in this specification are briefly outlined below.
That is, in the case of an aspect of the present invention, when selectively etching a silicon-oxide insulating film deposited on a semiconductor substrate through plasma-etching of the insulating film with a fluorocarbon-based gas and an etching gas containing oxygen, the insulating film is first etched by weakening the deposition property of a polymer layer and then etched by strengthening the deposition property of the polymer.
In the case of another aspect of the present invention, when selectively etching a silicon-oxide insulating film deposited on a semiconductor substrate through plasma-etching of the insulating film with a fluorocarbon-based gas and an etching gas containing oxygen, the insulating film is etched by changing etching conditions in accordance with the quantity of CF-based deposit.
In the case of still another aspect of the present invention, when selectively etching a silicon-oxide insulating film deposited on a semiconductor substrate through plasma-etching of the insulating film with a fluorocarbon-based gas and an etching gas containing oxygen and thereby, forming a hole or trench on the insulating film, comprising the steps of:
(a) forming up to the half depth of a hole or trench is executed by assuming the flow-rate ratio of the oxygen in the etching gas as a first flow-rate ratio in a first step, and
(b) forming the hole or trench is executed by applying etching while making the flow-rate ratio of the oxygen in the etching gas lower the first flow-rate ratio in a second step.
In the case of still another aspect of the present invention, when selectively etching a silicon-oxide insulating film deposited on a semiconductor substrate through plasma-etching of the insulating film with a fluorocarbon-based gas and an etching gas containing oxygen and thereby, forming a hole or trench on the insulating film, comprising the steps of:
(a) forming the hole or trench up to the half depth of it by assuming the bias power between upper and lower electrodes of the etching system as a first bias power in a fist step, and
(b) forming the hole or trench by executing etching while making the bias power between upper and lower electrodes of the etching system lower than the first bias power in a second step.
In the case of still another aspect of the present invention, the final aspect ratio of the hole or trench formed through the etching is larger than 12.
In the case of still another aspect of the present invention, the final aspect ratio of the hole or trench formed through the etching is larger than 14.
In the case of still another aspect of the present invention, the final aspect ratio of the hole or trench formed through the etching is larger than 16.
In the case of still another aspect of the present invention, the above fluorocarbon-base gas uses C5F3.
In the case of still another aspect of the present invention, the above etching gas contains argon gas.